Electric. Period. Our CD 22 didn't have them until I put the things on. Then I added a momentary switch by the port side seat so my wife could run her own. Even if it isn't raining, some well-placed splash and a slight breeze can drive you nuts. Our new boat has them already, but now I am bugging the electricians at work to scrounge up some time delay relays to add an intermittent feature.
A near future project is to tap into the pressure side of the demand pump I added to the freshwater system on board. I figure to run some 1/4" tubing to a small valve near the helm, and then to spray nozzles at the outside top of the front windows. Saltwater spray can really make a mess of things. Window washers aren't really all that necessary, but since the pressure system is there already, it is almost free.
Keep in mind, though, that I am kind of weird when it comes to electric gadgets.